Optical fiber connectors are a type of optical interface device used for optically joining fiber optical cables where connect and disconnect capability is required. The traditional and most common type of optical fiber connector uses a ferrule to hold one or more optical fibers. The ferrule has a slightly curved end so that when two connectors are mated, the ends of the fibers come into physical contact. One drawback of physical-contact connectors is that they are sensitive to contamination. The size of airborne dust is known to range from submicrons to tens of microns, which is comparable to the core diameter of both single-mode fibers and multi-mode fibers. In addition, dirt and debris can fully truncate the optical path between the connected fibers. Consequently, data transmission between connectors that employ physical contact between the fibers can easily be degraded due to contamination on the surfaces. Another disadvantage of physical-contact connectors is that precise alignment is critical for obtaining high coupling efficiency. A small angular or lateral misalignment between the fiber ends can be detrimental to the coupling efficiency.
Another type of optical fiber connector uses microlenses at the respective fiber ends to provide the optical connection between fiber ends, thereby avoiding the need for physical contact between the fibers. Such connectors are referred to as expanded-beam (EB) connectors because the light beam from the launch optical fiber is expanded and collimated by the first microlens of the launch connector and then focused by the second microlens of the receive connector. While many of the problems of physical-contact connectors can be avoided through the use of expanded-beam connectors, there is still a need for improvements in misalignment tolerance and coupling efficiency.